ls1leadfoot

iTrader: (1)

i am going from a ls1 to a lq4.....stock internals....
now will going from 10.5.1 down to 9.5.1 lower hp and make the car slower.....if not
how come everyone says c/r should be higher.....i do plan on running a wet nos kit after break in and tune....is that a good idea or not

s346k

iTrader: (4)

stock ls1 cr is 10.2:1 and stock lq4 cr is 9.4:1. i think the lower compression ratio would be made up by the difference in cubic inches - in your comparison. obviously more compression is going to generate more hp (and tq), but if you are getting into the motor during this build, why not do something to bump the compression up?

BIG_MIKE2005

iTrader: (116)

Thats a good FI ratio. I'd personally want it higher N/A & with nitrous. Nitrous loves compression also. I'm running right around 11.0:1 & I wouldn't go back ever unless I was goin boosted.

405HP_Z06

iTrader: (11)

Generally speaking, higher compression will produce higher horsepower. If your a light nitrous user or naturally aspirated, you should shoot for as close to 11.3:1 SCR as you can get.

Drew04GTO

iTrader: (1)

Fixed.

405HP_Z06

iTrader: (11)

Only if you subscribe to the DCR myth, I don't.

ls1leadfoot

iTrader: (1)

so high comp higher hp.....then will 9.5.1 take 10%----15% off what i could be making on top line numbers or like 10 20 hp........
i am at my whits end with engine.....dont have the 200.00 for .030 gaskets from cometic
stockers are 63.02 for the set
oh and the reason it;s too late to do it while im in the motor....is because the machine shop just assambeled and balanced the stock lq4 pistons in my build

s346k

iTrader: (4)

i think it's something like 7-8% increase/decrease in hp per point of compression. it's not like the car would go from mid 11s @ 9.5 cr to a 9 sec car @ 10.5...

it'll still make good power, just go with it and stop worrying.

ls1leadfoot

iTrader: (1)

haha....thats what i needed to hear...

THANKS GUYS!!!!!

Stang's Bane

iTrader: (22)

x2

That **** is so over hyped it is not even funny.

405HP_Z06

iTrader: (11)

Here's an excellent article by David Vizard on compression ratio. Vizard knows his stuff. He has a chart in the article that speaks to what your looking for. The power increase isn't a linear factor, but more a diminishing one the higher the compression.

http://www.popularhotrodding.com/tec...ech/index.html

Captain InsaneO

iTrader: (38)

I agree. I'm at 11.5:1 but my engine was built for nitrous. Regardless your engine will do fine on spray, but keep in mind a thinner head gasket is better for nitrous. Less of a chance to blow the head gasket. That's why I also went with cometic .030. Yes they were $180.00 but it's a little bit of insurance that my engine won't have any issues, and of course ARP head studs.

Sell a kidney and buy some cometics! lol

Grimes

iTrader: (3)

That's a really broad question, but like other said, generally the answer is yes lower compression is less power. (Assuming your CR is not so high that pinging is holding you back)

For example, if say you are running a blower and you cannot run as much advance with 10:1 vs. 9.1....you lower the CR, and you may make more power.

JScamaro

iTrader: (6)

I would not use that low of compression unless you are going with a turbo or supercharger.

Captain InsaneO

iTrader: (38)

What heads are you running? You could have them milled to bump up the compression some. I have mine down to 59cc's

ShevrolayZ28

iTrader: (4)

One point of compressioin is good for a HP difference of about 2%. So going from 11:1 to 10:1 in a 400 hp motor will result in around 10 less HP.

FMX05

iTrader: (3)

You should be fine man. Look at it this way, you can probably use 87 or 89 octane fuel. I'm at 12:1 and not looking back though...